In the manufacture of articles, such as metal articles, it is common for oil-based compositions to be used as lubricants and/or coolants during the manufacturing process. It is frequently necessary to clean such manufactured articles of the oil-based compositions prior to subsequent steps, such as coating or decorating surfaces of the article.
Commonly, such manufacturing oils are cleaned with either acidic or caustic solutions and subsequently rinsed with water for cleaning. Such cleaning processes have a number of disadvantages, including hazards in handling acidic or caustic solutions, the need for treatment of used wash solutions for compliance with environmental regulations prior to discharge of the used solutions and damage to the articles being cleaned.
It has been recognized in related applications that terpene-based cleaning compositions are particularly advantageous for cleaning oil-based compositions in the manufacture of articles. For example, in specific processes, such as the manufacture of cans, it has been found in the present invention that terpene-based cleaning compositions cause significantly less etching when compared with acidic or caustic wash solutions. Such reduced etching results in highly improved reflectivity of containers, increased mobility of articles on conveyor lines, and also allows for the recycle of various liquid streams in the cleaning system.
A problem encountered in terpene-based cleaning systems is that to recycle the cleaning solution, contaminants which have been removed from articles must be separated from the contaminated cleaning solution prior to recycling of the cleaning solution. However, it has been found that many terpene-based compositions do not allow for effective separation or release of contaminants, at least not quickly enough for most commercial manufacturing processes. For example, U.S. Pat. No. 4,511,488 (Matta 1985) discloses a d-limonene-based composition having between 10 and 60 volume percent d-limonene and between 10 and 30 volume percent surfactant. It has been found that compositions having surfactant levels in this range do not provide adequate releasability of contaminants for a suitable recycling process.
Thus, there is a need for an improved terpene-based cleaning process and composition which provides for effective cleaning, easy release of contaminants and improved recycling of liquid streams in a cleaning process.